1. Field of the Invention
Embodiments of the present invention relate to a display device, and more particularly, to an electrophoretic display device. Embodiments of the present invention are suitable for a wide range of applications. In particular, embodiments are suitable for decreasing a drive voltage of the electrophoretic display device.
2. Description of the Related Art
If a material having an electric charge is placed in DC electric field, the material moves in accordance with electric charges, the size and shape of molecules and the like. Such a movement, i.e., a phenomenon in which materials are separated by the difference of movement, is named ‘Electrophoresis.’ Recently, a display device using electrophoresis has been developed. The interest in the electrophoresis display device stems from its potential use as a substitute for conventional paper medium.
FIG. 1 shows a schematic diagram of a circuit for generating a data voltage waveform in an electrophoretic display device in accordance with the related art. A similar related art display device has been disclosed in U.S. Pat. Nos. 7,012,600 and 7,119,772. Referring to FIG. 1, the related art electrophoretic display device compares the data entered in the current state with the data to be entered in the next state for each cell by use of a lookup table (LUT) 1, a plurality of memories 2 to 4 and a frame counter 5, as shown in FIG. 1, thereby determining the data V1 to Vn which are to be supplied to each cell for a plurality of frame periods, as a result.
The data V1 to Vn outputted from the lookup table 1 are digital data such as ‘00’, ‘01’, ‘10’ and ‘11’, and are changed to voltages of three states which are applied to a pixel electrode of each cell. ‘00’ and ‘11’ in the digital data is changed to 0V, ‘01’ is changed to +15V, and ‘10’ is changed to −15V.
FIG. 2 shows data voltage waveforms in the lookup table shown in FIG. 1 in accordance with the related art. In FIG. 2, ‘W(11)’ represents a peak white gray level, ‘LG(10)’ represents a bright intermediate gray level, ‘DG(01)’ represents a dark intermediate gray level, and ‘B(00)’ represents a peak black gray level. And, the number written under the drive waveform is the number of frames during which a particular waveform is applied.
A DC common voltage Vcom is supplied to a common electrode which is opposite to a pixel electrode. A positive data voltage supplied to the pixel electrode is a voltage which is higher than the DC common voltage Vcom, and a negative data voltage is a voltage which is lower than the DC common voltage Vcom.
A driving method of the electrophoretic display device has several problems: firstly, the storage capacity of a memory 4 increases because the digital data of each cell is 2 bits; moreover, the data voltage changed in accordance with the digital data are +15V and −15V which are comparatively high; furthermore, elements within a data drive integrated circuit (D-IC) should be configured as high voltage elements because of a high data voltage, thus the size of the D-IC should be that much larger and the cost thereof increases.